Swinging or partner swapping (sometimes referred to as the swinging lifestyle or simply the lifestyle) is a non-monogamous behavior, in which partners in a committed relationship agree, as a couple, for both partners to engage in sexual activities with other people, sometimes referred to as recreational or social sex. Swinging can take place in a number of contexts, ranging from a spontaneous sexual activity at an informal social gathering of friends to a swingers' club and can involve internet-based introduction services.

The term wife swapping is now criticized as being androcentric and not accurately describing the full range of sexual activities in which couples may take part, but the term continues in use, and reflects the origins of the concept whereby husbands were viewed as initiating an informal partner swap.

As a general rule, swinging couples engage in conventional sexual activities, but with other partners. Penetrative sex by a swinging partner is referred to as a full swap; while non-penetrative sex, such as oral sex, is referred to as a soft swap. New swinging couples often choose a soft swap before they are comfortable with a full swap, although many couples stay "soft swap" for personal or safety related reasons. Soft swinging occurs when the couple engage in sexual activities while two or more other couples perform sex acts in the immediate vicinity.